The present invention relates to methods for determining bovine estrus, and more particularly to chemical techniques for ascertaining when artificial insemination is likely to produce offspring.
In order to increase milk production and maximize offspring in both dairy and beef cattle, detection of estrus and the use of artificial insemination are important to proper herd management. Detection of estrus has become more acute with increased dairy herd size, escalating labor costs, use of artificial insemination in beef herds, and with the use of loose housing systems for dairy cattle. Identification of one or more metabolites in a readily accessible body fluid would be an important step in detecting bovine estrus.
The importance of estrus detection in bovines, where reproduction is primarily based on artificial insemination, is well established (Manns and Hafs, 1976). This has led to a variety of attempts to establish a simple method to determine this important state. These have included studying cow mounting behavior in free ranging situations (Hurnik et al., 1975), the amount of movement displayed during the estrous cycle (as measured by a pedometer) (Kiddy, 1977) and measurement of electrical resistance of vaginal mucus (Gartland et al., 1976).
Sambras and Waring (1975) documented the ability of sexually experienced bulls to discriminate estrous females from non-estrous ones on the basis of urinary odors. In addition, Paleologou (1977) found that vaginal mucus from estrous cows would stimulate bulls to mount dummies used for semen collection. Mucus from non-estrous cows had no effect. Studies such as these suggest that bulls may base part of their discrimination between estrous and non-estrous cows on odors found in the genital region of female bovine. Consequently, while the role of behaviorally important odors from estrous cows in attracting bulls has not been definitely established, there is evidence for the existence of such odors.
An effort to document the types of compounds present in cow urine which might change during the estrous cycle was reported by Price and Manning (1978). Using a headspace concentration technique in combination with GC/MS, the concentration change in approximately 30 volatile compounds on a daily basis across 3 menstrual cycles from 1 non-lactating cow was examined. No reproducible changes were seen in the concentration of these volatiles, even though the cow displayed good estrous behavior.
Studies by Kiddy et al (1978, 1981) employing trained dogs, show that these animals can differentiate odors from a variety of bovine body fluids (blood, milk, urine, vaginal secretions) obtained from estrous and non-estrous cows. Hence, a quantitative and/or qualitative change in the volatiles from readily available sources were thought to be characteristic of estrus. Another recent investigation by Ladewig and Hart (1981) found that rats could be trained to detect estrous-related odors in cow urine. It is not surprising that the rats used in this study were able to find a difference in the urinary odor while instrumental methods were not, since mammalian olfactory abilities often exceed the instrumental sensitivity of a GC/MS used in the normal scanning mode. Each of these studies demonstrate that there is a characteristic change in excreted metabolites due to a change in hormonal state. However, it is not known if the dogs and rats are employing the same odors that bulls employ.
Some success has been achieved at predicting and determining ovulation in other species, particularly humans. Please refer to the disclosures of U.S. Pat. Nos. 3,986,494, 4,010,738 and 4,119,089. While the techniques of these disclosures are described as being applicable to livestock such as cows, the art has yet to identify or suggest the particular compositions disclosed herein as being useful in analytical technique to determine when a cow is in estrus.